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Kegan DougalandClaude Opus 5
cac8b6e343
A member key names no server, so a room full of them is a room whose members cannot be routed to, served to, or shown to anyone. What a key stands for is the linkage information on its `m.room.member` event, and this teaches the server to read it: another server's member can now join one of our member key rooms over federation, and we learn who they are from the event that put them there. A member key's link is the linkage information on its *current* `m.room.member` event, and nothing else. A member who has left has no link, because the event that removed them was somebody else's and asserts nothing about them. Making the mapping a function of the room's current state means every server that has the state agrees on it, no history is needed to compute it, and an event arriving late or by backfill cannot change it. Two signatures decide what a claim is worth. The member key's own makes the claim theirs, and without it the claim is ignored entirely: on an event the member sent, the `sender` signature is already that; on an event somebody else sent about them, it is the signature under `state_key`. The current server signing key of the claimed domain makes the claim *verified*, and that is the half that needs the network, so it is the half that can fail for reasons that are nobody's fault: a domain that does not answer leaves the link unverified rather than refused, and unverified links are re-checked on a small bounded loop so that a member whose server was briefly unreachable does not stay invisible until they next change their membership. What a link is used for depends on which half holds. The claimed domain is where the room's traffic goes, verified or not: an unverified claim is somewhere to send to, and grants nothing. Only a verified link makes a server a member server — able to be told the room's history, to be served its state, to be treated as present in it — because anybody can claim anybody's domain. Events from a key with no verified link are soft failed, so their state changes still count (membership and power levels are decided by keys, not by who holds them) but their messages are not shown to clients. Joining a room of this kind works from either end. A joining server does not know the room's version until `/make_join` answers, so it cannot know whether to name its user by ID or by key: it sends the user ID in the path and the key in `org.matrix.msc4430.member_key`, which a server that has never heard of MSC4430 ignores. The key is held in memory until the room turns out to want it, so joining a room without member keys leaves nothing behind, and it is stored before the join is sent, so a join that succeeds is never one we cannot sign for afterwards. A resident server accepts a key in either place and refuses a bare user ID for such a room. Because the sender of a membership event is a key and not a user ID, the check that the sender belongs to the requesting server no longer applies: the origin is simply who relayed it, and what the member claims about their own server is in the event, signed by them. The end-to-end tests build the remote half by hand, so that a server can be made to vouch for its member, decline to, vouch for a different one, or lie about somebody else's. They cover a verified join, an unverified one, a re-check that succeeds on a later attempt, a member key that moves to another server and takes its member with it, and a moderator who bans a member while naming a domain they control and changes nothing about who that member is. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
.. image:: https://github.com/element-hq/synapse/raw/develop/docs/element_logo_white_bg.svg :height: 60px **Element Synapse - Matrix homeserver implementation** |support| |development| |documentation| |license| |pypi| |python| Synapse is an open source `Matrix <https://matrix.org>`__ homeserver implementation, written and maintained by `Element <https://element.io>`_. `Matrix <https://github.com/matrix-org>`__ is the open standard for secure and interoperable real-time communications. You can directly run and manage the source code in this repository, available under an AGPL license (or alternatively under a commercial license from Element). There is no support provided by Element unless you have a subscription from Element. 🚀 Getting started ================== This component is developed and maintained by `Element <https://element.io>`_. It gets shipped as part of the **Element Server Suite (ESS)** which provides the official means of deployment. ESS is a Matrix distribution from Element with focus on quality and ease of use. It ships a full Matrix stack tailored to the respective use case. There are three editions of ESS: - `ESS Community <https://github.com/element-hq/ess-helm>`_ - the free Matrix distribution from Element tailored to small-/mid-scale, non-commercial community use cases - `ESS Pro <https://element.io/server-suite>`_ - the commercial Matrix distribution from Element for professional use - `ESS TI-M <https://element.io/server-suite/ti-messenger>`_ - a special version of ESS Pro focused on the requirements of TI-Messenger Pro and ePA as specified by the German National Digital Health Agency Gematik 🛠️ Standalone installation and configuration ============================================ The Synapse documentation describes `options for installing Synapse standalone <https://element-hq.github.io/synapse/latest/setup/installation.html>`_. See below for more useful documentation links. - `Synapse configuration options <https://element-hq.github.io/synapse/latest/usage/configuration/config_documentation.html>`_ - `Synapse configuration for federation <https://element-hq.github.io/synapse/latest/federate.html>`_ - `Using a reverse proxy with Synapse <https://element-hq.github.io/synapse/latest/reverse_proxy.html>`_ - `Upgrading Synapse <https://element-hq.github.io/synapse/develop/upgrade.html>`_ 🎯 Troubleshooting and support ============================== 🚀 Professional support ----------------------- Enterprise quality support for Synapse including SLAs is available as part of an `Element Server Suite (ESS) <https://element.io/pricing>`_ subscription. If you are an existing ESS subscriber then you can raise a `support request <https://customer.element.io/support>`_ and access the `Element product documentation <https://docs.element.io>`_. 🤝 Community support -------------------- The `Admin FAQ <https://element-hq.github.io/synapse/latest/usage/administration/admin_faq.html>`_ includes tips on dealing with some common problems. For more details, see `Synapse's wider documentation <https://element-hq.github.io/synapse/latest/>`_. For additional support installing or managing Synapse, please ask in the community support room |room|_ (from a matrix.org account if necessary). We do not use GitHub issues for support requests, only for bug reports and feature requests. .. |room| replace:: ``#synapse:matrix.org`` .. _room: https://matrix.to/#/#synapse:matrix.org .. |docs| replace:: ``docs`` .. _docs: docs 🛠️ Development ============== We welcome contributions to Synapse from the community! The best place to get started is our `guide for contributors <https://element-hq.github.io/synapse/latest/development/contributing_guide.html>`_. This is part of our broader `documentation <https://element-hq.github.io/synapse/latest>`_, which includes information for Synapse developers as well as Synapse administrators. Developers might be particularly interested in: * `Synapse's database schema <https://element-hq.github.io/synapse/latest/development/database_schema.html>`_, * `notes on Synapse's implementation details <https://element-hq.github.io/synapse/latest/development/internal_documentation/index.html>`_, and * `how we use git <https://element-hq.github.io/synapse/latest/development/git.html>`_. Alongside all that, join our developer community on Matrix: `#synapse-dev:matrix.org <https://matrix.to/#/#synapse-dev:matrix.org>`_, featuring real humans! Copyright and Licensing ======================= | Copyright 2014–2017 OpenMarket Ltd | Copyright 2017 Vector Creations Ltd | Copyright 2017–2025 New Vector Ltd | Copyright 2025 Element Creations Ltd This software is dual-licensed by Element Creations Ltd (Element). It can be used either: (1) for free under the terms of the GNU Affero General Public License (as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version); OR (2) under the terms of a paid-for Element Commercial License agreement between you and Element (the terms of which may vary depending on what you and Element have agreed to). Unless required by applicable law or agreed to in writing, software distributed under the Licenses is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the Licenses for the specific language governing permissions and limitations under the Licenses. Please contact `licensing@element.io <mailto:licensing@element.io>`_ to purchase an Element commercial license for this software. .. |support| image:: https://img.shields.io/badge/matrix-community%20support-success :alt: (get community support in #synapse:matrix.org) :target: https://matrix.to/#/#synapse:matrix.org .. |development| image:: https://img.shields.io/matrix/synapse-dev:matrix.org?label=development&logo=matrix :alt: (discuss development on #synapse-dev:matrix.org) :target: https://matrix.to/#/#synapse-dev:matrix.org .. |documentation| image:: https://img.shields.io/badge/documentation-%E2%9C%93-success :alt: (Rendered documentation on GitHub Pages) :target: https://element-hq.github.io/synapse/latest/ .. |license| image:: https://img.shields.io/github/license/element-hq/synapse :alt: (check license in LICENSE file) :target: LICENSE .. |pypi| image:: https://img.shields.io/pypi/v/matrix-synapse :alt: (latest version released on PyPi) :target: https://pypi.org/project/matrix-synapse .. |python| image:: https://img.shields.io/pypi/pyversions/matrix-synapse :alt: (supported python versions) :target: https://pypi.org/project/matrix-synapse